Techniques for using active amplitude modulation for simultaneous determination of range and velocity in an fmcw lidar system

ABSTRACT

A light detection and ranging (LIDAR) system has an active modulator to modulate a light signal from an optical source with a low-power mode at a section of a sweep signal to generate a pulsed light signal transmitted towards a target. The LIDAR system has a photodetector to receive a return beam from the target with an amplitude modulated (AM) signal portion and a frequency modulated (FM) signal portion. The LIDAR system determines a target range value for the target based on the AM signal portion and determines a target velocity value for the target based on the FM signal portion.

RELATED APPLICATIONS

This application is a continuation of, and claims priority to, U.S.application Ser. No. 17/512,569 filed Oct. 27, 2021, now U.S. Pat. No.11,435,453, which in turn is a nonprovisional application based on, andclaims priority to, U.S. Provisional Application No. 63/175,414 filedApr. 15, 2021. That provisional application is incorporated herein byreference.

This application is related to U.S. patent application Ser. No.17/512,570, titled: TECHNIQUES FOR SIMULTANEOUS DETERMINATION OF RANGEAND VELOCITY WITH PASSIVE MODULATION, and U.S. patent application Ser.No. 17/512,576, titled: TECHNIQUES FOR DETECTION PROCESSING WITHAMPLITUDE MODULATION (AM) AND FREQUENCY MODULATION (FM) PATHS FORSIMULTANEOUS DETERMINATION OF RANGE AND VELOCITY, both filed Oct. 27,2021.

FIELD

Descriptions are generally related to light scanning systems, and moreparticularly, coherent LIDAR (light detection and ranging) systems.

BACKGROUND

Some light scanning systems, such as frequency-modulated continuous-wave(FMCW) LIDAR systems, utilize “upchirp” (or “up sweep”) and downchirp(or “down sweep”) signals to capture information related to surroundingtargets. However, in some scenarios, waiting for these signals to betransmitted and received can limit the ability of these systems toquickly and efficiently obtain target information, such as velocity,range, or other information, or a combination of information. Inaddition, these light scanning systems can alias short range targetswhich can lead to disambiguation issues.

BRIEF DESCRIPTION OF THE DRAWINGS

The following description includes discussion of figures havingillustrations given by way of example of an implementation. The drawingsshould be understood by way of example, and not by way of limitation. Asused herein, references to one or more examples are to be understood asdescribing a particular feature, structure, or characteristic includedin at least one implementation of the invention. Phrases such as “in oneexample” or “in an alternative example” appearing herein provideexamples of implementations of the invention, and do not necessarily allrefer to the same implementation. However, they are also not necessarilymutually exclusive.

FIG. 1 illustrates an example LIDAR system.

FIG. 2 represents a time-frequency diagram illustrating an example ofLIDAR waveform detection and processing.

FIG. 3 illustrates an example of a LIDAR system with active modulationto provide a combined FM and AM signal.

FIG. 4 illustrates an example of a LIDAR system with active modulationand a reference loop to provide a combined FM and AM signal.

FIG. 5A illustrates an example of a LIDAR signal with FM modulationselectively turned off in the middle of a down sweep.

FIG. 5B illustrates an example of a LIDAR signal and its reflection withFM modulation selectively in low power at a beginning of a down sweep.

FIG. 6 illustrates an example of a LIDAR signal selectively in low powerat the beginning of a down sweep and a beginning of an up sweep.

FIG. 7 illustrates an example of modulation signals for on/offmodulation.

FIG. 8 illustrates an example of a LIDAR signal and its reflection for aLIDAR signal selectively in low power at the beginning of a down sweepand a beginning of an up sweep.

FIG. 9 illustrates an example of a LIDAR system with active modulationto provide a combined FM and AM signal on a transmit path.

FIG. 10 illustrates an example of a LIDAR system with active modulationto provide a combined FM and AM signal on a transmit path with areference detector.

FIG. 11A illustrates an example of an AM signal with on/off modulationwith local oscillator and transmit paths modulated.

FIG. 11B illustrates an example of an AM signal with a modulationwaveform with local oscillator and transmit paths modulated.

FIG. 12A illustrates an example of an AM signal with on/off modulationwith only a transmit path modulated.

FIG. 12B illustrates an example of an AM signal with a modulationwaveform with only a transmit path modulated.

FIG. 13 illustrates an example of a LIDAR system with active AMmodulation for a multipath system.

FIG. 14 illustrates an example of a LIDAR system with passive modulationto provide a combined FM and AM signal.

FIG. 15 illustrates an example of a LIDAR system with passive modulationto provide a combined FM and AM signal on a transmit path with areference detector.

FIG. 16 illustrates an example an AM signal based on passive modulationto provide a combined FM and AM signal.

FIG. 17 illustrates an example of a LIDAR system with passive AMmodulation for a multipath system.

FIG. 18 illustrates an example of a LIDAR system with an IQimplementation to distinguish AM information from FM information for aLIDAR signal.

FIG. 19 illustrates an example of a LIDAR system that provides FM and AMmodulation on a LIDAR signal.

FIG. 20 illustrates an example of FQ detection for a LIDAR system thatprovides FM and AM modulation on a LIDAR signal.

FIG. 21 illustrates an example of signal processing for an FM and AMmodulated signal.

FIG. 22 illustrates an example of an AM path and an FM path for I/Qdetection.

FIG. 23 illustrates an example of an AM path and an FM path for FQdetection with combined time domain filters.

FIG. 24 illustrates an example of in-phase detection for an FM and AMmodulated LIDAR signal.

FIG. 25 illustrates an example of joint estimation from AM and FMdatapaths for concurrent range and velocity estimation.

FIG. 26 illustrates an example an FM datapath processing for frequencypeak selection.

FIG. 27 illustrates an example an AM datapath processing for time domaincorrelation.

FIG. 28 illustrates an example of AM datapath processing for time domaincorrelation when only a transmit path is modulated.

FIG. 29 illustrates an example of delay estimation for AM signalcorrelation.

FIG. 30 illustrates an example of a LIDAR system that provides FM and AMmodulation on a LIDAR signal.

Descriptions of certain details and implementations follow, includingnon-limiting descriptions of the figures, which may depict some or allexamples, as well as other potential implementations.

DETAILED DESCRIPTION

As described herein, a frequency-modulated continuous-wave (FMCW) lightdetection and ranging (LIDAR) system provides amplitude modulation (AM)or time of flight (TOF) signaling to a frequency modulation (FM)modulated light signal. The application of AM modulation or TOFsignaling to the FMCW signal enables range and velocity measurementsimultaneously from the return signal.

A LIDAR system can provide TOF information with an FM modulated signalor frequency modulated signal as a power and frequency modulated signal.When the power and frequency modulated signal is transmitted to atarget, the system can process reflection signals from the target togenerate a point set (e.g., data point cloud, target point set, and thelike). The target point set processing can include frequency processingto generate target points based on range and Doppler information, andTOF processing to provide TOF range information. The LIDAR system cangenerate an FM modulated signal and provide the FM modulated signal withTOF signal information via an active modulator or a passive modulator.The combined signal is a power and frequency modulated signal.

According to some examples, the described LIDAR system may beimplemented in any sensing market, such as, but not limited to,transportation, manufacturing, metrology, medical, augmented reality,virtual reality, and security systems. According to some examples, thedescribed LIDAR system is implemented as part of a front-end offrequency modulated continuous-wave (FMCW) device that assists withspatial awareness for automated driver assist systems or self-drivingvehicles, such as part of an automobile, motorcycle, bicycle, scooter,helicopter, or plane, or other vehicle.

FIG. 1 illustrates an example LIDAR system. The LIDAR system 100includes one or more of each of a number of components, but may includefewer or additional components than what is illustrated. One or more ofthe components depicted in LIDAR system 100 can be implemented on aphotonics chip, according to some examples. As shown, the LIDAR system100 includes optical circuits 112 implemented on a photonics chip. Inone example, optical circuits 112 include active optical components. Inone example, optical circuits include passive optical components. In oneexample, optical circuits 112 include a combination of active opticalcomponents and passive optical components. Active optical componentsrefer to components that can generate, amplify, or detect opticalsignals, or perform a combination of generate, amplify, or detect. Insome examples, the active optical component performs operations onoptical beams at different wavelengths, and includes one or more opticalamplifiers, one or more optical detectors, or other components toperform operations on the light signal.

Free space optics 132 refers to one or more components that can carryoptical signals and route and manipulate optical signals betweenappropriate input or output ports of the optical circuit and thecomponents of the optical circuit. In one example, free space optics 132includes one or more optical components such as taps, wavelengthdivision multiplexers (WDM), splitters/combiners, polarization beamsplitters (PBS), collimators, couplers, or other components to direct anoptical signal. In some examples, free space optics 132 includescomponents to transform the polarization state and direct receivedpolarized light, for example, to optical detectors using a PBS. In oneexample, free space optics 132 includes a diffractive element to deflectoptical beams having different frequencies at different angles along anaxis (e.g., a fast axis).

In some examples, LIDAR system 100 includes optical scanner 142 thatincludes one or more scanning mirrors that are rotatable along an axis(e.g., a slow axis) that is orthogonal or substantially orthogonal tothe fast axis of the diffractive element. Optical scanner 142 can steeroptical signals to scan an environment according to a scanning pattern.For instance, the scanning mirrors can be rotatable by one or moregalvanometers. Incident light from a source optical signal tends toscatter off objects in a target environment, generating a return opticalbeam or a target return signal. Optical scanner 142 can collect thereturn optical beam or the target return signal and provide the returnsignal for processing. Optical scanner 142 can return the signal topassive optical circuit components or active optical circuit componentsof optical circuits 112. For example, free space optics 132 can direct asignal to an optical detector via a polarization beam splitter. Inaddition to mirrors and galvanometers, examples of optical scanner 142can include components such as a quarter-wave plate, lens,anti-reflective coated window, or other component to receive an opticalsignal.

To control and support optical circuits 112 and optical scanner 142,LIDAR system 100 includes LIDAR control system 120. LIDAR control system120 includes a signal processor, control component, or other device toprocess control operations for LIDAR system 100. The signal processorrepresents a processing device to control the operation of LIDAR system100. The signal processor can be or include, for example, one or moregeneral-purpose processing devices such as a microprocessor, centralprocessing unit, processing component, or other controller/processor.The signal processor can be, for example, a complex instruction setcomputing (CISC) microprocessor, a reduced instruction set computer(RISC) microprocessor, a very long instruction word (VLIW)microprocessor, or a processor implementing other instruction sets, orprocessors implementing a combination of instruction sets. In oneexample, the signal processor can be or include one or morespecial-purpose processing devices such as an application specificintegrated circuit (ASIC), a field programmable gate array (FPGA), adigital signal processor (DSP), network processor, or other computationcomponent.

In some examples, LIDAR control system 120 includes signal processingunit 122. Signal processing unit 122 represents a processing devicespecific for performing signal computations. For example, signalprocessing unit 122 can be a DSP. LIDAR control system 120 can beconfigured to output digital control signals to control optical drivers114. In some examples, the digital control signals can be converted toanalog signals through signal conversion unit 116. For example, signalconversion unit 116 can include a digital-to-analog converter (DAC).Optical drivers 114 can provide drive signals to active opticalcomponents of optical circuits 112 to drive optical sources such aslasers and amplifiers. In some examples, several optical drivers 114 andsignal conversion units 116 can be provided to drive multiple opticalsources.

LIDAR control system 120 can be configured to output digital controlsignals for optical scanner 142. Motion control system 150 can controlgalvanometers or other movable components of optical scanner 142 basedon control signals received from LIDAR control system 120. For example,a DAC can convert coordinate routing information from LIDAR controlsystem 120 to signals interpretable by galvanometers in optical scanner142. In some examples, motion control system 150 can return informationto LIDAR control system 120 about the position or operation ofcomponents of optical scanner 142. For example, an analog-to-digitalconverter (ADC) can convert information about a galvanometer's positionto a signal interpretable by LIDAR control system 120.

LIDAR control system 120 can be configured to analyze incoming digitalsignals. In this regard, LIDAR system 100 includes free opticalreceivers 134 to measure one or more beams received by free space optics132, which can also be passed to optical circuits 112. For example, areference beam receiver can measure the amplitude of a reference beamfrom an active optical component, and an ADC converts signals from thereference receiver to signals interpretable by LIDAR control system 120.Target receivers measure the optical signal that carries informationabout the range and velocity of a target in the form of a beatfrequency, modulated optical signal. The reflected beam can be mixedwith a signal from a local oscillator. Optical receivers 134 can includea high-speed ADC to convert signals from the target receiver to signalsinterpretable by LIDAR control system 120. In some examples, signalconditioning unit 136 can perform signal conditioning on signals fromoptical receivers 134 prior to receipt by LIDAR control system 120. Forexample, the signals from optical receivers 134 can be provided to anoperational amplifier (op-amp) for amplification of the return signalsand the amplified signals can be provided to LIDAR control system 120.

In some applications, LIDAR system 100 includes one or more imagingdevices 160 configured to capture images of the environment, globalpositioning system (GPS) 180 configured to provide a geographic locationof the system, or other sensor inputs. Image processing system 170represents one or more components configured to receive the images fromimaging devices 160 or geographic location from GPS 180 and prepare theinformation for receipt and use by LIDAR control system 120 or othersystem connected to LIDAR system 100. For example, image information canbe pre-processed for use by LIDAR control system 120. In anotherexample, location information can be formatted for use by LIDAR system100.

In some examples, the scanning process begins with optical drivers 114and LIDAR control system 120. LIDAR control system 120 can instructoptical drivers 114 to independently modulate one or more optical beams,and these modulated signals propagate through the optical circuit to acollimator. The collimator directs the light at the optical scanningsystem that scans the environment over a preprogrammed pattern definedby motion control system 150. Optical circuits 112 can include apolarization wave plate (PWP) to transform the polarization of the lightas it leaves optical circuits 112. In some examples, the polarizationwave plate can be a quarter-wave plate or a half-wave plate. A portionof the polarized light can be reflected back to optical circuits 112.For example, lensing or collimating systems used in LIDAR system 100 canhave natural reflective properties or a reflective coating to reflect aportion of the light back to optical circuits 112.

Optical signals reflected back from the environment pass through opticalcircuits 112 to the receivers. If the polarization of the light has beentransformed, it can be reflected by a polarization beam splitter (PBS)along with the portion of polarized light that was reflected back tooptical circuits 112. Accordingly, rather than returning to the samefiber or waveguide as an optical source, the reflected light isreflected to separate optical receivers. These signals interfere withone another and generate a combined signal. Each beam signal thatreturns from the target produces a time-shifted waveform. The temporalphase difference between the two waveforms generates a beat frequencymeasured on the optical receivers (photodetectors). The combined signalcan then be reflected to optical receivers 134.

Optical receivers 134 can apply ADCs to convert the analog signals fromoptical receivers to digital signals. The digital signals are then sentto LIDAR control system 120. Signal processing unit 122 can receive thedigital signals and interpret them. In some examples, signal processingunit 122 also receives position data from motion control system 150 andgalvanometers (not shown) as well as image data from image processingsystem 170. Signal processing unit 122 can then generate a 3D pointcloud with information about range and velocity of points in theenvironment as optical scanner 142 scans additional points. Signalprocessing unit 122 can also overlay a 3D point cloud data with theimage data to determine velocity and distance of objects in thesurrounding area. In one example, LIDAR system 100 processessatellite-based navigation location data to provide a precise globallocation.

In operation according to some examples, LIDAR system 100 is configuredto simulate aspects of time of flight signal processing by performingamplitude modulation on a frequency modulated source signal to enablemeasurement of time of flight as well as range and velocitysimultaneously from the return signal.

In one example, the FM signal can include TOF information by loweringpower or powering off the beam going towards a target for a limitedportion of the frequency sweep. In one example, the power is reduced toa low power modulation (TPower Low) during the sweep. In one example,the low power state can be when the modulation is turned off (TPowerOff) during the sweep. In one example, the power can be in low power oroff state at the beginning of the sweep. In one example, the power canbe in low power or off state at the beginning of the up sweep and at thebeginning of the down sweep. As one or more beam reflections come backfrom the target, the TPower signal can be offset in time (TTOF or timeof the time of flight signal) with a value corresponding to the range ofthe object based, at least in part, on one or more signal propagationdelays between LIDAR system 100 and one or more targets. Thus, in thisfashion, signal conversion unit 116 and optical drivers 114 can modulateTOF information onto an FMCW signal. Optical circuits 112 and free spaceoptics 132 can send the signal to the environment for scanning. One ormore circuits, units, systems, or devices of LIDAR system 100 can enterlow power mode before, during, and/or after the TPower signal.

Return signals received through free space optics 132 and free spaceoptical receivers 134 can be processed with signal conditioning 136 andprocessed by LIDAR control system 120. Signal processing unit 122 cancompute a TTOF and provide a range measurement that is not a function ofDoppler, while the beat frequency is a function of range and Doppler.LIDAR system 100 can be configured to perform range and Dopplercalculation with a single measurement by combining the information ofthe TTOF and beat frequency.

In one example, the FM signal can include AM modulation of any type. TheAM modulation can be or include passive modulation or active modulation.The AM information can be extracted separately from the FM modulation,enabling the system to perform range and Doppler determinationconcurrently. FM modulation low power or power off (TPower Low) can beconsidered a specific case of AM modulation on the FMCW signal. In somescenarios, signals transmitted and/or processed by LIDAR system 100 caninclude any type of FM and AM modulation.

In one example, the system computes an estimate of the range using atime domain processing datapath including a correlator and a delayestimator. The estimate of range in combination with frequency domainpeaks leads to a more robust estimate of range and velocity per point.As stated above, the system can provide the modulation actively orpassively. The active modulation can be active amplitude modulation withan active amplitude modulator. The passive modulation can be passiveamplitude modulation with a passive amplitude modulator. For activemodulation, the system can provide modulation using a Mach-Zehndermodulator (MZM), modulating optical amplifier gain signal, amplifiergain signal, an optical attenuator, attenuator, laser AM modulation,saturable absorber, optical switch, or other active modulator.

In some scenarios, only the transmit signal (TX) or transmit path ismodulated. In such a case, the TTOF can be calculated from theelectrical signal on an MZM or OA and the low TPower of the received(RX) signal. In some scenarios, the modulation is done in both the TXand local oscillator (LO) path. In such a case, the TTOF can beextracted from the difference in LO and RX signal.

In some scenarios, modulation is done using passive modulation. Forexample, the system can apply a Mach-Zehnder interferometer (MZI). Thesystem can apply another type of passive amplitude modulation. Thesystem can extract the TOF data from the RX+LO modulation. In somescenarios, the AM part of the FM modulation can be extracted using anI/Q detector.

FIG. 2 represents a time-frequency diagram illustrating an example ofLIDAR waveform detection and processing. Diagram 200 represents atime-frequency diagram of an FMCW scanning signal 210 that can be usedby a LIDAR system, such as system 100, to scan a target environmentaccording to some examples. In one example, the scanning waveform 210,labeled as f_(FM)(t), is a sawtooth waveform (sawtooth “chirp”) with achirp bandwidth Δf_(C) and a chirp period T_(C).

The slope of the sawtooth is given as k=(Δf_(C)/T_(C)). Diagram 200 alsodepicts target return signal 220 according to some examples. Targetreturn signal 220, labeled as f_(FM)(t−Δt), is a time-delayed version ofscanning signal 210, where Δt is the roundtrip time to and from a targetilluminated by scanning signal 210. The roundtrip time is given asΔt=2R/v, where R is the target range, and v is the velocity of theoptical beam, which is the speed of light c. The target range, R, cantherefore be calculated as R=c(Δt/2).

When return signal 220 is optically mixed with scanning signal 210, arange-dependent difference frequency, referred to as the beat frequency,Δf_(R)(t) is generated. The beat frequency Δf_(R)(t) is linearly relatedto the time delay, Δt, by the slope of the sawtooth k. Thus,Δf_(R)(t)=kΔt. Since the target range R is proportional to Δt, thetarget range R can be calculated as R=(c/2)(Δf_(R)(t)/k). Thus, therange R is linearly related to the beat frequency Δf_(R)(t).

The beat frequency Δf_(R)(t) can be generated, for example, as an analogsignal in optical receivers 134 of system 100. The beat frequency canthen be digitized by an ADC, for example, in a signal conditioning unitsuch as signal conditioning unit 136 in LIDAR system 100. The digitizedbeat frequency signal can then be digitally processed, for example, in asignal processing unit, such as signal processing unit 122 in system100.

It will be understood that target return signal 220 will, in general,also include a frequency offset (Doppler shift) if the target has avelocity relative to the LIDAR system. The Doppler shift can bedetermined separately, and used to correct the frequency of the returnsignal, so the Doppler shift is not shown in diagram 200 for simplicityand ease of explanation. It should also be noted that the samplingfrequency of the ADC will determine the highest beat frequency that canbe processed by the system without aliasing. In general, the highestfrequency that can be processed is one-half of the sampling frequency(i.e., the “Nyquist limit”).

In one example, and without limitation, if the sampling frequency of theADC is 1 gigahertz, then the highest beat frequency that can beprocessed without aliasing (Δf_(Rmax)) is 500 megahertz. This limit inturn determines the maximum range of the system asRmax=(c/2)(Δf_(Rmax)/k) which can be adjusted by changing the chirpslope k. In one example, while the data samples from the ADC may becontinuous, the subsequent digital processing described below may bepartitioned into “time segments” that can be associated with someperiodicity in the LIDAR system. In one example, and without limitation,a time segment might correspond to a predetermined number of chirpperiods T, or a number of full rotations in azimuth by the opticalscanner.

FIG. 3 illustrates an example of a LIDAR system with active modulationto provide a combined FM and AM signal according to embodiments of thepresent disclosure. System 300 illustrates a LIDAR system that mayinclude one or more functions included in LIDAR system 100. System 300can include separate processing components (not specifically shown). Forinstance, according to some embodiments, PBS 360 and optics 304 can beportions of free space optics 132. Laser 310, modulator 320, andcombiner 340 can be portions of optical circuits 112. Detectors 352, 354can be portions of free space optical receivers 134.

System 300 includes at least one laser 310 which includes thefunctionality to produce a light signal that is processed by one or moreoptical circuit elements of the optical circuitry of circuit 302.Circuit 302 can include modulator 320 to modulate the light signaltransmitted from laser 310. In one example, laser 310 is acontinuous-wave laser. In one example, modulator 320 is an SOA(semiconductor optical amplifier). The modulation techniques performedby modulator 320 can include, but is not limited to, FM modulation, AMmodulation, and the like. In one scenario, modulator 320 can be orinclude an FM modulator to FM modulate the source signal. In anotherscenario modulator 320 includes an amplification component.

In one example, modulator 320 includes the functionality to performmodulation procedures within and/or using a lower power mode provided byone or more components providing power supply to LIDAR system 300.Examples of low power include, but are not limited to, sleep modes,standby modes, or similar power states. In one scenario, modulator 320,using one or more active modulator components within, can modulate lightsignals received to produce a power and FM signal and/or AM signal. Inone example, the TOF signal information provided by modulator 320includes an AM signal modulated onto the FM modulated signal. In oneexample, modulator 320 is an active modulator. The modulator 320 can beor include, for example, a Mach-Zehnder modulator (MZM). The modulator320 can be or include, for example, an optical attenuator. The modulator320 can be or include, for example, an optical circuit to AM modulate anoptical amplifier gain signal.

Splitter 330 represents a splitter or optical coupler to steer themodulated optical signal to optical transmit components and a local pathfor beam combining. Thus, splitter 330 can split the modulated signal tosend the signal along a transmit (TX) path to a circulator or PBS(polarized beam splitter) 360 that emits the modulated LIDAR signalthrough free space optics 304.

PBS 360 and optics 304 can represent an optical emitter to emit thepower and frequency modulated signal from system 300. Optics 304 and PBS360 can also represent receiver components to receive a reflection ofthe emitted LIDAR signal. The received reflection signal can be routedthrough PBS 360 or circulator to optical combiner 340.

Combiner 340 can receive a reference signal from splitter 330 and thereflection signal from PBS 360. Combiner 340 provides the signals to oneor more photodetectors, identified as detector 352 and detector 354.Detector 352 and detector 354 can provide the signal information to oneor more processing components. Circuit 302 can provide optical signalinformation to a processor or component for final signal processing.

The processing components, based on the signals from the detectors fromcircuit 302, can extract TOF information from an AM modulated signal anddetermine the range and velocity of targets identified in the scanningusing an FM modulated signal. The processing components can map targetswith a point set with per point information based on the combined AM andFM signal.

The processing components (not specifically shown) receive detectedsignal information from detector 352 and detector 354 and apply signalprocessing on the reflection signal to generate a target point set. Theprocessing can include frequency processing to generate target pointsbased on range and Doppler information. The processing can also includeTOF processing to provide TOF range information.

FIG. 4 illustrates an example of a LIDAR system with active modulationand a reference loop to provide a combined FM and AM signal. System 400illustrates a LIDAR system in accordance with embodiments of the presentdisclosure. System 400 can include separate processing components (notspecifically shown).

System 400 includes laser 410, which includes the functionality toproduce a light signal that is processed by one or more optical circuitelements of the optical circuitry of circuit 402. Circuit 402 caninclude modulator 420 to modulate the light signal transmitted fromlaser 410. In one example, laser 410 is a continuous-wave laser. In oneexample, modulator 420 is an SOA (semiconductor optical amplifier). Themodulation techniques performed by modulator 420 can include FMmodulation, AM modulation, or other modulation. In one example,modulator 420 can include an FM modulator to FM modulate the sourcesignal. In one example, modulator 420 includes an amplificationcomponent.

In one example, modulator 420 includes one or more active modulatorcomponents to provide TOF signal information with the FM modulatorsignal, to generate a power and frequency modulated signal or FM and AMmodulated signal. In one example, the modulation includes amplitudemodulation. In one example, the TOF signal information provided bymodulator 420 includes an AM signal modulated onto the FM modulatedsignal. In one example, modulator 420 is an active modulator. Themodulator 420 can be or include, for example, a Mach-Zehnder modulator(MZM). The modulator 420 can be or include, for example, an opticalattenuator. The modulator 420 can be or include, for example, an opticalcircuit to AM modulate an optical amplifier gain signal.

An example of system 400 includes reference (REF) loop 480. Thus, thelaser signal from laser 410 can be split with splitter 470 into areference delay loop and a phased-lock loop (PLL) to be linearlychirped. Reference loop 480 can provide a reference source signal priorto modulation of the signal for purposes of combining for processing.

The frequency modulated laser can be fed into modulator 420, which canrepresent an optical amplifier or power modulator. The power andfrequency or AM and FM modulated light can be split to two paths bysplitter 430, one for the local oscillator (LO) and one for thetransmitter (TX). PBS 460 represents a PBS or circulator followed byother optical elements (integrated or free space optics) to emit themodulated LIDAR signal through free space optics 404. Optics 404 and PBS460 can couple back the return signal (RX) from the target and combinewith the LO using an optical combiner, represented by combiner 440.

Combiner 440 can receive a reference signal from splitter 430 and thereflection signal from PBS 460. Combiner 440 provides the signals to oneor more photodetectors, identified as detector 452 and detector 454.Detector 452 and detector 454 can provide the signal information to oneor more processing components. Circuit 402 can provide optical signalinformation to a processor or component for final signal processing.

The processing components, based on the signals from the detectors fromcircuit 402, can separate an amplitude modulation signal portion and anFM modulation portion. The processing components can extract TOFinformation from the AM modulation and determine the range and velocityof targets from the FM modulation. The processing components can maptargets with a point set with per point information based on thecombined AM and FM signal.

The processing components (not specifically shown) receive detectedsignal information from detector 452 and detector 454 and apply signalprocessing on the reflection signal to generate a target point set. Theprocessing can include frequency processing to generate target pointsbased on range and Doppler information. The processing can also includeTOF processing to provide TOF range information.

FIG. 5A illustrates an example of a LIDAR signal with FM modulationselectively turned off in the middle of a down sweep. Diagram 502represents an example of a signal and the reflection of the signal.Diagram 502 represents signaling in accordance with embodiments of thepresent disclosure.

The rising frequency (FREQ) over time represents an up sweep of thesignal frequency, and the decreasing frequency over time represents adown sweep of the signal frequency. Diagram 502 represents an example ofencoding time of flight information by turning off the power of themodulation for a period T_low (time of low modulation power).

Signal 510 represents a transmit or TX signal, identified as f_(FM)(t).Signal 510 is represented as the solid line and has a pattern of upsweep, followed by a down sweep, followed by an up sweep. Signal 520represents a receive or reflection signal or RX signal, identified asf_(FM)(t−Δt), where Δt represents the total time of flight for thesignal to transmit to the target, and for a reflection to return fromthe target. Signal 520 is represented as the dashed line and also has apattern of up sweep, followed by a down sweep, followed by an up sweep.

In some cases, T_low (e.g., low power or power off) occurs during thesweeps when the laser frequency is in a stable value. An estimate of therange can be obtained using a time domain processing data path includinga correlator and a delay estimator to measure Δt. The estimate of range,in combination with frequency domain peaks, leads to a more robustestimate of range and velocity per point.

Time 512, labeled as P_(LOW_TX), represents the time when the transmitsignal modulation has low power. Time 512 occurs during the down sweep.Time 522, labeled as P_(LOW_RX), represents the time when the reflectionsignal modulation has low power. The time Δt is the time between thetransmit signal being emitted and the reflection signal being receivedand detected. The processing device can determine Δt by computing thelow power time in the RX signal as compared to the low power time in theTX signal.

Thus, in one example, the optical circuitry of a LIDAR device canselectively reduce FM modulation to low power or turn frequencymodulation off for a pulse. The pulse of frequency modulation willappear in the receive signal, and correlation of the two signals canidentify the time of flight. In one example, as in diagram 502, thefrequency modulation can be adjusted to low power for a pulse during afrequency down sweep.

FIG. 5B illustrates an example of a LIDAR signal and its reflection withFM modulation selectively at low power at a beginning of a down sweep.Diagram 504 represents an example of a signal and the reflection of thesignal. Diagram 504 represents signaling in accordance with embodimentsof the present disclosure.

The rising frequency (FREQ) over time represents an up sweep of thesignal frequency, and the decreasing frequency over time represents adown sweep of the signal frequency. Diagram 504 represents an example ofencoding time of flight information by turning off the power of themodulation for a period T_low (time of low modulation power).

Signal 530 represents a transmit or TX signal, identified as f_(FM)(t).Signal 530 is represented as the solid line and has a pattern of upsweep, followed by a down sweep, followed by an up sweep. Signal 540represents a receive or reflection signal or RX signal, identified asf_(FM)(t−Δt), where Δt represents the total time of flight for thesignal to transmit to the target, and for a reflection to return fromthe target. Signal 540 is represented as the dashed line and also has apattern of up sweep, followed by a down sweep, followed by an up sweep.

In some cases, T_low occurs in between the sweeps when the laserfrequency is in transition. As illustrated, T_low occurs at thetransition between up sweep and down sweep. An estimate of the range canbe obtained using a time domain processing data path including acorrelator and a delay estimator to measure ΔT. The estimate of range,in combination with frequency domain peaks, leads to a more robustestimate of range and velocity per point.

Time 532, labeled as P_(LOW_TX), represents the time when the transmitsignal modulation has low power or the modulation power is off. Time 532occurs during a transition from up sweep to down sweep. Time 542,labeled as P_(LOW_RX), represents the time when the reflection signalmodulation has low power or the modulation power is off. The time Δt isthe time between the transmit signal being emitted and the reflectionsignal being received and detected. The processing device can determineΔt by computing the low power time in the RX signal as compared to thelow power time in the TX signal.

Thus, in one example, the optical circuitry of a LIDAR device canselectively adjust FM modulation to low power or turn frequencymodulation off for a pulse. The pulse of frequency modulation willappear in the receive signal, and correlation of the two signals canidentify the time of flight. In one example, as in diagram 504, thefrequency modulation can be adjusted to low power for a pulse at abeginning of a transition from frequency up sweep to frequency downsweep.

FIG. 6 illustrates an example of a LIDAR signal selectively in low powerat the beginning of a down sweep and a beginning of an up sweep. Diagram602 represents an example of a signal and the reflection of the signal.Diagram 602 represents signaling in accordance with embodiments of thepresent disclosure.

The rising frequency (FREQ) over time represents an up sweep of thesignal frequency, and the decreasing frequency over time represents adown sweep of the signal frequency. Diagram 602 represents an example ofencoding time of flight information by turning off the power of themodulation for a period T_low (time of low modulation power). The periodis a section of the sweep signal.

Signal 610 represents a transmit or TX signal. In some cases, T_lowoccurs in between the sweeps when the laser frequency is in transition.As illustrated, T_low occurs at the transition between up sweep (orupsweep or upsweep signal) and down sweep (or downsweep or downsweepsignal) and at the transition between down sweep and up sweep.

Time 612, labeled as P_(LOW), represents the time when the transmitsignal modulation has low power at a transition between up sweep anddown sweep. Time 614, also labeled as P_(LOW), represents the time whenthe reflection signal modulation has low power at a transition betweendown sweep and up sweep.

Thus, in one example, the optical circuitry of a LIDAR device canselectively turn FM modulation to low power or turn frequency modulationoff for a pulse. The pulse of frequency modulation will appear in thereceive signal, and correlation of the two signals can identify the timeof flight. In one example, as in diagram 602, the frequency modulationcan be adjusted to low power for a pulse at a beginning of a transitionfrom frequency up sweep to frequency down sweep and from a transitionfrom frequency down sweep to frequency up sweep.

Diagram 604 illustrates the power or AM signal for the signal of diagram602. The power can be observed to be in low power when the modulation isat low modulation power. Thus, power 620 represents the modulationsignal power modulated onto the carrier light signal. Power 622represents the P_(LOW) times.

FIG. 7 illustrates an example of modulation signals for on/offmodulation. On/off modulation refers to modulation that changes from abaseline modulation power to a low modulation power state or themodulation power is reduced (which may be reduced all the way to zeropower). Diagram 702 represents an example of a signal (TX) and thereflection (RX) of the signal. Diagram 702 represents time of flightsignaling by way of selectively reducing modulation power for a periodor by turning modulation frequency off.

The solid triangle signal represents the transmit signal TX. The TXsignal has a T_low at 720 in the up sweep of the TX signal, and has aT_low at 730 in the next up sweep of the TX signal. The dashed linetriangle signal represents the reflection signal RX. The RX signal has aT_low period at 722 corresponding to the T_low at 720 in the TX signal.The RX signal has a T_low period 732 corresponding to the T_low at 730in the TX signal. The period ΔT is represented as the time between theTX T_low and the RX T_low.

Diagram 704 provides a representation of the modulation signal ofdiagram 702. In diagram 702, the T_low time at 710 corresponds to T_lowtime 720 of the TX signal. Similarly, the T_low time at 712 correspondsto T_low time 730 of the TX signal. As the beam comes back from thetarget, the T_low will be offset in time (ΔT) with a value correspondingto the range of the object. Measuring the total time of flight TToF (ΔT)provides a range measurement that is not a function of Doppler, whilethe beat frequency from the frequency modulated signal is a function ofRange and Doppler. Combining the information of the TToF and beatfrequency allows for range and doppler calculation within a singlemeasurement.

The selective transitioning between the baseline modulation power andthe low power modulation (at T_low) can be referred to as a low powermode. An active modulator can have a low power mode to enabletransitioning between normal power operation and low power operation orturning off modulation power. The low power mode provides lower power inthe FM modulation to generate a TOF information detectable in a returnbeam that reflects off a target or target environment that is scannedwith the optical beam. The optical light source can provide FMmodulation and the low-power mode can provide time of flightinformation. The LIDAR system can provide a first portion of the lightsignal for a sweep signal to generate a pulsed light transmitted towardthe target, and a second portion of the light signal for a localoscillator. The first and second portions of the light signal can bedetected from the return beam, enabling detection of range and velocityfrom a single optical beam.

FIG. 8 illustrates an example of a LIDAR signal and its reflection for aLIDAR signal selectively set to low power at the beginning of a downsweep and a beginning of an up sweep. Diagram 802 represents an exampleof a signal and the reflection of the signal. Diagram 802 representssignaling in accordance with an embodiments of the present disclosure.

The rising frequency (FREQ) over time represents an up sweep of thesignal frequency, and the decreasing frequency over time represents adown sweep of the signal frequency. Diagram 802 represents an example ofencoding time of flight information by turning the power of themodulation to lower power for a period T_low (time of low modulationpower).

Signal 810 represents a transmit or TX signal, identified as f_(FM)(t).Signal 810 is represented as the solid line and has a pattern of upsweep, followed by a down sweep, followed by an up sweep. Signal 820represents a receive or reflection signal or RX signal, identified asf_(FM)(t−Δt), where Δt represents the total time of flight for thesignal to transmit to the target, and for a reflection to return fromthe target. Signal 820 is represented as the dashed line and also has apattern of up sweep, followed by a down sweep, followed by an up sweep.

In some cases, T_low occurs in between the sweeps when the laserfrequency is in transition. As illustrated, T_low occurs at thetransition between up sweep and down sweep and at the transition betweendown sweep and up sweep. Time 812, labeled as P_(LOW_TX), represents thetime when the transmit signal modulation has low power or the power iszero or off at a transition between up sweep and down sweep. Time 822,labeled as P_(LOW_RX), represents the time when the reflection signalmodulation has low power or the power is zero or off.

Time 814, labeled as P_(LOW_TX), represents the time when the transmitsignal modulation has low power at a transition between down sweep andup sweep. Time 814 occurs during a transition from up sweep to downsweep. Time 824, labeled as P_(LOW_RX), represents the time when thereflection signal modulation has low power for the transition of the TXsignal between down sweep and up sweep.

The time TTOF is the Δt, or the time between the transmit signal beingemitted and the reflection signal being received and detected. Theprocessing device can determine Δt by computing the low power time inthe RX signal as compared to the low power time in the TX signal.

In some cases, T_low occurs in between the sweeps when the laserfrequency is in transition. As illustrated, T_low occurs at thetransition between up sweep and down sweep and at the transition betweendown sweep and up sweep. An estimate of the range can be obtained usinga time domain processing data path including a correlator and a delayestimator to measure ΔT. The estimate of range, in combination withfrequency domain peaks, leads to a more robust estimate of range andvelocity per point.

Diagram 804 illustrates the power or AM signal for the signal of diagram802. The power can be observed to be in low power when the modulation isat low power, and is identified as T_(PWR_LOW). Baseline 830 representsthe modulation signal power modulated onto the carrier light signal.Zero 832 represents the P_(LOW) time for the transition between up sweepand down sweep. Zero 834 represents the P_(LOW) time for the transitionbetween down sweep and up sweep.

FIG. 9 illustrates an example of a LIDAR system with active modulationto provide a combined FM and AM signal on a transmit path. System 900illustrates a LIDAR system in accordance with embodiments of the presentdisclosure. System 900 can include separate processing components (notspecifically shown).

System 900 illustrates laser 910, which includes the functionality toproduce a light signal that is processed by one or more optical circuitelements of the optical circuitry of circuit 902. Circuit 902 caninclude modulator 920 to modulate the light signal transmitted fromlaser 910. In one example, laser 910 is a continuous-wave laser. In oneexample, modulator 920 is an SOA (semiconductor optical amplifier). Themodulation techniques performed by modulator 920 can include FMmodulation, AM modulation, or other modulation. In one example,modulator 920 can include an FM modulator to FM modulate the sourcesignal. In one example, modulator 920 includes an amplificationcomponent.

In one example, modulator 920 includes one or more active modulatorcomponents to provide TOF signal information with the FM modulatorsignal, to generate a power and frequency modulated signal or FM and AMmodulated signal. In one example, the modulation includes amplitudemodulation. In one example, the TOF signal information provided bymodulator 920 includes an AM signal modulated onto the FM modulatedsignal. In one example, modulator 920 is an active modulator. The activemodulator can be or include, for example, a Mach-Zehnder modulator(MZM). The active modulator can be or include, for example, an opticalattenuator. The active modulator can be or include, for example, anoptical circuit to AM modulate an optical amplifier gain signal. Thefrequency modulated laser can be fed into modulator 920, which canrepresent an optical amplifier or power modulator.

An example of system 900 includes reference (REF) loop 980. Thus, thelaser signal from laser 910 can be split with splitter 970 into areference delay loop and a phased-lock loop (PLL) to be linearlychirped. Reference loop 980 can provide a reference source signal priorto modulation of the signal for purposes of combining for processing.

In some scenarios, only the TX signal is power modulated. In this casethe TTOF can be calculated from the electrical signal on the MZM or OAand the TPower low of a received (RX) signal. As illustrated in system900, only the TX power is modulated and the LO signal is received fromsplitter 970 after laser 910, without being modulated by modulator 920.Modulator 920 thus only modulates the transmit path, with the LO pathsplitting off before the modulation. In such a case, the TOF delay canbe measured by clocking the input electrical signal into the modulatorand received signal.

The power and frequency or AM and FM modulated light can be sent to PBS960, which represents a PBS or circulator followed by other opticalelements (integrated or free space optics) to emit the modulated LIDARsignal through free space optics 904. Optics 904 and PBS 960 can coupleback the return signal (RX) from the target and combine with the LOusing an optical combiner, represented by combiner 940. Combiner 940 canreceive a reference signal from splitter 970 and the reflection signalfrom PBS 960. Combiner 940 provides the signals to one or morephotodetectors, identified as detector 952 and detector 954. Detector952 and detector 954 can provide the signal information to one or moreprocessing components. Circuit 902 can provide optical signalinformation to a processor or component for final signal processing.

The processing components, based on the signals from the detectors fromcircuit 902, can extract amplitude modulation or TOF information from FMmodulation and determine the range and velocity of targets identified inthe scanning. The processing components can map targets with a point setwith per point information based on the combined AM and FM signal.

The processing components (not specifically shown) receive detectedsignal information from detector 952 and detector 954 and apply signalprocessing on the reflection signal to generate a target point set. Theprocessing can include frequency processing to generate target pointsbased on range and Doppler information. The processing can also includeTOF processing to provide TOF range information.

FIG. 10 illustrates an example of a LIDAR system with active modulationto provide a combined FM and AM signal on a transmit path with areference detector. System 1000 illustrates a LIDAR system in accordancewith embodiments of the present disclosure. System 1000 can includeseparate processing components (not specifically shown).

System 1000 includes laser 1010, which includes functionality to producea light signal that is processed by one or more optical circuit elementsof the optical circuitry of circuit 1002. Circuit 1002 can includemodulator 1020 to modulate the light signal transmitted from laser 1010.In one example, laser 1010 is a continuous-wave laser. In one example,modulator 1020 is an SOA (semiconductor optical amplifier). Themodulation techniques performed by modulator 1020 can include FMmodulation, AM modulation, or other modulation, modulator 1020 caninclude an FM modulator to FM modulate the source signal. In oneexample, modulator 1020 includes an amplification component.

In one example, modulator 1020 includes one or more active modulatorcomponents to provide TOF signal information with the FM modulatorsignal, to generate a power and frequency modulated signal or FM and AMmodulated signal. In one example, the modulation includes amplitudemodulation. In one example, the TOF signal information provided bymodulator 1020 includes an AM signal modulated onto the FM modulatedsignal. In one example, modulator 1020 is an active modulator. Theactive modulator can be or include, for example, a Mach-Zehndermodulator (MZM). The active modulator can be or include, for example, anoptical attenuator. The active modulator can be or include, for example,an optical circuit to AM modulate an optical amplifier gain signal. Thefrequency modulated laser can be fed into modulator 1020, which canrepresent an optical amplifier or power modulator.

An example of system 1000 includes reference (REF) loop 1082. Thus, thelaser signal from laser 1010 can be split with splitter 1080 into areference delay loop and a phased-lock loop (PLL) to be linearlychirped. Reference loop 1082 can provide a reference source signal priorto modulation of the signal for purposes of combining for processing.

In some scenarios, only the TX signal is power modulated. In this casethe TTOF can be calculated from the electrical signal on the MZM or OAand the TPower low of a received (RX) signal. As illustrated in system1000, only the TX power is modulated and the LO signal is received fromsplitter 1080 after laser 1010, without being modulated by modulator1020. Modulator 1020 thus only modulates the transmit path, with the LOpath splitting off before the modulation. In such a case, the TOF delaycan be measured by clocking the input electrical signal into themodulator and received signal.

The power and frequency or AM and FM modulated light can be sent to PBS1060, which represents a PBS or circulator followed by other opticalelements (integrated or free space optics) to emit the modulated LIDARsignal through free space optics 1004. Optics 1004 and PBS 1060 cancouple back the return signal (RX) from the target and combine with theLO using an optical combiner, represented by combiner 1040. Combiner1040 can receive a reference signal from splitter 1080 and thereflection signal from PBS 1060. Combiner 1040 provides the signals toone or more photodetectors, identified as detector 1052 and detector1054. Detector 1052 and detector 1054 can provide the signal informationto one or more processing components. Circuit 1002 can provide opticalsignal information to a processor or component for final signalprocessing.

An example of system 1000 includes splitter 1070 to split the power andfrequency modulated signal in the transmit path to PBS 1060 and todetector 1072. As illustrated in circuit 1002, modulator 1020 canreceive AM electrical (ELEC) signal 1022 as a signal to provide onto thefrequency modulated light signal. Detector 1072 generates electrical(ELEC) signal 1074 that can be used as a reference by the processingcomponents. Detector 1052 and detector 1054 also generate outputelectrical (ELEC) signals 1056 to be processed by the processingcomponents.

The processing components, based on the signals from the detectors fromcircuit 1002, can extract amplitude modulation or TOF information fromFM modulation and determine the range and velocity of targets identifiedin the scanning. The processing components can map targets with a pointset with per point information based on the combined AM and FM signal.

The processing components (not specifically shown) receive detectedsignal information from detector 1052, detector 1054, and detector 1072and apply signal processing on the reflection signal to generate atarget point set. The processing can include frequency processing togenerate target points based on range and Doppler information. Theprocessing can also include TOF processing to provide TOF rangeinformation.

FIG. 11A illustrates an example of an AM signal with on/off modulationwith local oscillator and transmit paths modulated. Diagram 1102illustrates an AM signal with on/off modulation with both the transmitpath (TX) and the local oscillator path (LO) modulated. Diagram 1102illustrates the sweep duration with signal pulses generated by applyingperiods of low power frequency modulation. Signal 1110 represents the AMsignal. T_low_LO 1120 represents the signal fed to the combiner from theinternal optical circuits, and T_low_RX 1130 represents the reflectionsignal received at the combiner after a time Delta_T later.

FIG. 11B illustrates an example an of AM signal with a modulationwaveform with local oscillator and transmit paths modulated. Diagram1104 illustrates an AM signal with an AM modulation waveform with LO andTX modulated. Diagram 1104 represents the signal detection in the RXpath of the TX signal of diagram 1102. Signal curve 1150 represents theTX modulation waveform. Signal curve 1140 represents the AM signalobtained by combining the received signal (RX waveform) with the localoscillator signal (RX*LO).

FIG. 12A illustrates an example of an AM signal with on/off modulationwith only a transmit path modulated. Diagram 1202 illustrates an AMsignal with on/off modulation with only the transmit path (TX)modulated. Diagram 1202 illustrates the sweep duration with a signalpulse generated by applying periods of low power frequency modulation.Signal 1210 represents the AM signal. T_low_RX 1220 represents thereflection signal received at the combiner.

FIG. 12B illustrates an example of an AM signal with a modulationwaveform with only a transmit path modulated. Diagram 1204 illustratesan AM signal with an AM modulation waveform with only TX modulated.Diagram 1204 represents the signal detection in the RX path of the TXsignal of diagram 1202. Signal curve 1250 represents the TX modulationwaveform. Signal curve 1240 represents the AM signal obtained from thereceived signal (RX waveform).

FIG. 13 illustrates an example of a LIDAR system with active AMmodulation for a multipath system. System 1300 illustrates a LIDARsystem in accordance with embodiments of the present disclosure. System1300 represents multiple instances of components in accordance with anexample of system 400. It will be understood that the use of multiplebeams can be implemented for any instance of optical circuit described,and for simplicity, only the configuration of multiple optical circuitsin accordance with system 400 is illustrated. The modulation formultiple beams can be performed with passive or with active modulationcomponents.

System 1300 can include separate processing components (not specificallyshown). System 1300 includes laser 1310, which includes thefunctionality to produce a light signal that is processed by multipleoptical circuits 1390 of the optical circuitry of circuit 1302.

Each optical circuit 1390 can include modulator 1320 to modulate thesource signal transmitted from laser 1310. In one example, laser 1310 isa continuous-wave laser. In one example, modulator 1320 is an SOA(semiconductor optical amplifier). The modulation techniques performedby modulator 1320 can include FM modulation, AM modulation, or othermodulation. In one example, modulator 1320 can include an FM modulatorto FM modulate the source signal. In one example, modulator 1320includes an amplification component.

In one example, modulator 1320 includes one or more active modulatorcomponents to provide TOF signal information with the FM modulatorsignal, to generate a power and frequency modulated signal or FM and AMmodulated signal. In one example, the modulation includes amplitudemodulation. In one example, the TOF signal information provided bymodulator 1320 includes an AM signal modulated onto the FM modulatedsignal. In one example, modulator 1320 is an active modulator. Theactive modulator can be or include, for example, a Mach-Zehndermodulator (MZM). The active modulator can be or include, for example, anoptical attenuator. The active modulator can be or include, for example,an optical circuit to AM modulate an optical amplifier gain signal.

An example of system 1300 includes reference (REF) loop 1380. Referenceloop 1380 can be common to all circuits 1390. The laser signal fromlaser 1310 can be split with splitter 1370 into a reference delay loopand a phased-lock loop (PLL) to be linearly chirped. Reference loop 1380can provide a reference source signal prior to modulation of the signalfor purposes of combining for processing. The splitter taps off thelaser light signal to the reference loop and to multiple beamforming andreceiver/detector circuits.

The frequency modulated laser can be fed into modulator 1320, which canrepresent an optical amplifier or power modulator. The power andfrequency or AM and FM modulated light can be split to two paths bysplitter 1330, one for the local oscillator (LO) and one for thetransmitter (TX). PBS 1360 represents a PBS or circulator followed byother optical elements (integrated or free space optics) to emit themodulated LIDAR signal through free space optics 1304. Optics 1304 andPBS 1360 can couple back the return signal (RX) from the target andcombine with the LO using an optical combiner, represented by combiner1340.

Combiner 1340 can receive a reference signal from splitter 1330 and thereflection signal from PBS 1360. Combiner 1340 provides the signals toone or more photodetectors, identified as detector 1352 and detector1354. Detector 1352 and detector 1354 can provide the signal informationto one or more processing components. Circuit 1302 can provide opticalsignal information to a processor or component for final signalprocessing.

The processing components, based on the signals from the detectors fromcircuit 1302, can extract amplitude modulation or TOF information fromFM modulation and determine the range and velocity of targets identifiedin the scanning. The processing components can map targets with a pointset with per point information based on the combined AM and FM signal.In one example, the same processing components can be used for parallelsignal processing for the parallel optical circuits 1390.

The processing components (not specifically shown) receive detectedsignal information from detector 1352 and detector 1354 and apply signalprocessing on the reflection signal to generate a target point set. Theprocessing can include frequency processing to generate target pointsbased on range and Doppler information. The processing can also includeTOF processing to provide TOF range information.

A multiple beam circuit can include a single laser and reference loop,with common optics for the multiple beams. The use of multiple transmitand receive/detection circuits can allow different beam steering andsweeping of different areas. In one example, the various transmit andreceive paths provided by circuits 1390 can be integrated onto the sameintegrated circuit or chip. In one example, the various transmit andreceive paths of circuits 1390 can be implemented as discrete componentscombined in parallel with common source and reference signals. In oneexample, different instances of optical circuits 1390 can implementdifferent types of modulation. Thus, multiple beams can combine anyexample of active or passive modulation structures.

In addition to multiple beams, or alternatively to multiple beams,different LIDAR systems can be used in parallel. For example, lasershaving different wavelengths can be used in parallel to perform sensingof a target.

FIG. 14 illustrates an example of a LIDAR system with passive modulationto provide a combined FM and AM signal. System 1400 illustrates a LIDARsystem in accordance with embodiments of the present disclosure. System1400 can include separate processing components (not specificallyshown).

System 1400 includes laser 1410, which includes the functionality toproduce a light signal that is processed by one or more optical circuitelements of the optical circuitry of circuit 1402. Circuit 1402 caninclude passive MZI 1420 to modulate the light signal transmitted fromlaser 1410. While represented as passive MZI, it will be understood thatpassive MZI 1420 can generally represent a passive modulator. In oneexample, laser 1410 is a continuous-wave laser. In one example, circuit1402 includes a modulator to FM modulate the optical signal. In oneexample, the optical signal is generated with FM modulation by laser1410. In one example, passive MZI 1420 includes one or more passivemodulator components to encode the FM modulated signal with an AMsignal, to generate an FM and AM modulated signal or AM and FM modulatedsignal.

An example of system 1400 includes reference (REF) loop 1482. Thus, thelaser signal from laser 1410 can be split with splitter 1480 into areference delay loop and a phased-lock loop (PLL) to be linearlychirped. Reference loop 1482 can provide a reference source signal priorto modulation of the signal for purposes of combining for processing.

The frequency modulated laser can be fed into passive MZI 1420, whichcan represent passive modulation for circuit 1402. The AM and FMmodulated light can be split to two paths by splitter 1430, one for thelocal oscillator (LO) and one for the transmitter (TX). PBS 1460represents a PBS or circulator followed by other optical elements(integrated or free space optics) to emit the modulated LIDAR signalthrough free space optics 1404. Optics 1404 and PBS 1460 can couple backthe return signal (RX) from the target and combine with the LO using anoptical combiner, represented by combiner 1440.

In one example, passive MZI 1420 does not perform amplification of thesignal. SOA (semiconductor optical amplifier) 1470 can provide opticalamplification for the signal in the transmit path. Splitter 1430 canprovide the AM and FM modulated signal to SOA 1470 for amplification,and SOA 1470 can provide the amplified signal to PBS 1460 to be emittedthrough optics 1404.

Combiner 1440 can receive a reference signal from splitter 1430 and thereflection signal from PBS 1460. Splitter 1430 can provide the FM and AMmodulated signal as a local oscillator (LO) signal for processing bydetector 1452 and detector 1454. Combiner 1440 provides the signals toone or more photodetectors, identified as detector 1452 and detector1454. Detector 1452 and detector 1454 can provide the signal informationto one or more processing components. Circuit 1402 can provide opticalsignal information to a processor or component for final signalprocessing.

The processing components, based on the signals from the detectors fromcircuit 1402, can extract AM information from FM modulation anddetermine the range and velocity of targets identified in the scanning.The processing components can map targets with a point set with perpoint information based on the combined AM and FM signal.

The processing components (not specifically shown) receive detectedsignal information from detector 1452 and detector 1454 and apply signalprocessing on the reflection signal to generate a target point set. Theprocessing can include frequency processing to generate target pointsbased on range and Doppler information. The processing can also includeTOF processing to provide TOF range information based on the AMmodulation of the reflection signal.

FIG. 15 illustrates an example of a LIDAR system with passive modulationto provide a combined FM and AM signal on a transmit path with areference detector. System 1500 illustrates a LIDAR system in accordancewith embodiments of the present disclosure. System 1500 can includeseparate processing components (not specifically shown).

System 1500 includes laser 1510, which includes the functionality toproduce a light signal that is processed by one or more optical circuitelements of the optical circuitry of circuit 1502. Circuit 1502 caninclude passive MZI 1530 to modulate the light signal transmitted fromlaser 1510. While represented as passive MZI, it will be understood thatpassive MZI 1530 can generally represent a passive modulator. In oneexample, laser 1510 is a continuous-wave laser. In one example, circuit1502 includes a modulator to FM modulate the optical signal. In oneexample, the optical signal is generated with FM modulation by laser1510. In one example, passive MZI 1530 includes one or more passivemodulator components to encode the FM modulated signal with an AMsignal, to generate an FM and AM modulated signal or AM and FM modulatedsignal.

An example of system 1500 includes reference (REF) loop 1582. Thus, thelaser signal from laser 1510 can be split with splitter 1580 into areference delay loop and a phased-lock loop (PLL) to be linearlychirped. Reference loop 1582 can provide a reference source signal priorto modulation of the signal for purposes of combining for processing.

In some scenarios, only the TX signal is power modulated. In this casethe TTOF can be calculated from the electrical signal based on the AMmodulation of the RX signal. As illustrated in system 1500, only the TXpower is modulated and the LO signal is received from splitter 1520after laser 1510, without being modulated by passive MZI 1530. PassiveMZI 1530 thus only modulates the transmit path, with the LO pathsplitting off before the modulation. In such a case, the TOF delay canbe measured by clocking the input electrical signal into the modulatorand received signal.

The frequency modulated laser can be fed from splitter 1520 into passiveMZI 1530, which can represent passive modulation for circuit 1502. TheAM and FM modulated light can be split to two paths by splitter 1520,one for the LO signal and one for the TX path. PBS 1560 represents a PBSor circulator followed by other optical elements (integrated or freespace optics) to emit the modulated LIDAR signal through free spaceoptics 1504. Optics 1504 and PBS 1560 can couple back the RX signal fromthe target and combine with the LO using an optical combiner,represented by combiner 1540.

In one example, passive MZI 1530 does not perform amplification of thesignal. SOA (semiconductor optical amplifier) 1570 can provide opticalamplification for the signal in the transmit path. Passive MZI 1530 canprovide the AM and FM modulated signal to SOA 1570 for amplification,and SOA 1570 can provide the amplified signal to PBS 1560 to be emittedthrough optics 1504.

Combiner 1540 can receive a reference signal from splitter 1520 and thereflection signal from PBS 1560. Splitter 1520 can provide the FM and AMmodulated signal as an LO signal for processing by detector 1552 anddetector 1554. Combiner 1540 provides the signals to one or morephotodetectors, identified as detector 1552 and detector 1554. Detector1552 and detector 1554 can provide the signal information to one or moreprocessing components. Circuit 1502 can provide optical signalinformation to a processor or component for final signal processing.

An example of system 1500 includes detector 1532, which receives themodulated signal from passive MZI 1530. Detector 1532 can generate anelectrical signal that can be used as a reference by the processingcomponents. Detector 1552 and detector 1554 also generate outputelectrical signals to be processed by the processing components.

The processing components, based on the signals from the detectors fromcircuit 1502, can extract amplitude modulation or TOF information fromFM modulation and determine the range and velocity of targets identifiedin the scanning. The processing components can map targets with a pointset with per point information based on the combined AM and FM signal.

The processing components (not specifically shown) receive detectedsignal information from detector 1552, detector 1554, and detector 1532and apply signal processing on the reflection signal to generate atarget point set. The processing can include frequency processing togenerate target points based on range and Doppler information. Theprocessing can also include TOF processing to provide TOF rangeinformation from the AM modulation on the RX signal.

FIG. 16 illustrates an example an AM signal based on passive modulationto provide a combined FM and AM signal. Diagram 1602 represents time offlight signaling by way of providing passive AM modulation. Signal 1610is represented by a solid line triangle signal, which represents thetransmit signal TX. The TX signal has FM modulation and AM modulation.Signal 1620 is represented by a dashed line triangle signal, whichrepresents the reflection signal RX.

As the beam comes back from the target, the RX signal will be offset intime (Δt) with a value corresponding to the range of the object.Measuring the total time of flight TToF (Δt) provides a rangemeasurement that is not a function of Doppler, while the beat frequencyfrom the frequency modulated signal is a function of Range and Doppler.Combining the information of the TToF and beat frequency allows forrange and doppler calculation within a single measurement.

Diagram 1604 provides a representation of the passive modulation signalof diagram 1602. Diagram 1604 is represented as a passive MZI signal.Signal 1630 is a power modulation (MOD) or AM modulated signal to encodeonto the carrier FMCW signal.

Diagram 1606 provides a representation of the passive modulation signaland the FM modulation signal overlayed on the same graph. Diagram 1606represents an RX signal having the FM RF (radio frequency) carrierfrequency and the AM modulation. Signal 1640 represents the reflectedpower modulation (MOD) AM signal. Signal 1650 represents the FM RFsignal of the RX signal.

Diagram 1604 and diagram 1606 provide a representation of the Δt of theRX signal. Signal 1630 of diagram 1604 has a peak amplitude (AMP), asdoes the AM signal 1640 of diagram 1606. The time difference between thepeak of signal 1630 and the peak of signal 1640 is Δt TOF (time offlight) 1660. Thus, the peaks of the AM signals can be used to detectthe range information from the RX signal.

FIG. 17 illustrates an example of a LIDAR system with passive AMmodulation for a multipath system. System 1700 illustrates a LIDARsystem in accordance with embodiments of the present disclosure. System1700 represents multiple instances of components in accordance with anexample of system 1400. It will be understood that the use of multiplebeams can be implemented for any instance of optical circuit described,and for simplicity, only the configuration of multiple optical circuitsin accordance with system 1400 is illustrated. The modulation formultiple beams can be performed with passive or with active modulationcomponents.

System 1700 can include separate processing components (not specificallyshown). System 1700 includes laser 1710, which includes thefunctionality to produce a light signal that is processed by multipleoptical circuits 1790 of the optical circuitry of circuit 1702.

Each optical circuit 1790 of circuit 1702 can include passive MZI 1720to modulate the light signal transmitted from laser 1710. In oneexample, laser 1710 is a continuous-wave laser. While represented aspassive MZI, it will be understood that passive MZI 1720 can generallyrepresent a passive modulator. In one example, laser 1710 is acontinuous-wave laser. In one example, circuit 1702 includes a modulatorto FM modulate the optical signal. In one example, the optical signal isgenerated with FM modulation by laser 1710. In one example, passive MZI1720 includes one or more passive modulator components to encode the FMmodulated signal with an AM signal, to generate an FM and AM modulatedsignal or AM and FM modulated signal.

An example of system 1700 includes reference (REF) loop 1782. Thus, thelaser signal from laser 1710 can be split with splitter 1780 into areference delay loop and a phased-lock loop (PLL) to be linearlychirped. Reference loop 1782 can provide a reference source signal priorto modulation of the signal for purposes of combining for processing.

The frequency modulated laser can be fed into passive MZI 1720, whichcan represent passive modulation for circuit 1702. The AM and FMmodulated light can be split to two paths by splitter 1730, one for thelocal oscillator (LO) and one for the transmitter (TX). PBS 1760represents a PBS or circulator followed by other optical elements(integrated or free space optics) to emit the modulated LIDAR signalthrough free space optics 1704. Optics 1704 and PBS 1760 can couple backthe return signal (RX) from the target and combine with the LO using anoptical combiner, represented by combiner 1740.

In one example, passive MZI 1720 does not perform amplification of thesignal. SOA (semiconductor optical amplifier) 1770 can provide opticalamplification for the signal in the transmit path. Splitter 1730 canprovide the AM and FM modulated signal to SOA 1770 for amplification,and SOA 1770 can provide the amplified signal to PBS 1760 to be emittedthrough optics 1704.

Combiner 1740 can receive a reference signal from splitter 1730 and thereflection signal from PBS 1760. Splitter 1730 can provide the FM and AMmodulated signal as a local oscillator (LO) signal for processing bydetector 1752 and detector 1754. Combiner 1740 provides the signals toone or more photodetectors, identified as detector 1752 and detector1754. Detector 1752 and detector 1754 can provide the signal informationto one or more processing components. Circuit 1702 can provide opticalsignal information to a processor or component for final signalprocessing.

The processing components, based on the signals from the detectors fromcircuit 1702, can extract AM information from FM modulation anddetermine the range and velocity of targets identified in the scanning.The processing components can map targets with a point set with perpoint information based on the combined AM and FM signal.

The processing components (not specifically shown) receive detectedsignal information from detector 1752 and detector 1754 and apply signalprocessing on the reflection signal to generate a target point set. Theprocessing can include frequency processing to generate target pointsbased on range and Doppler information. The processing can also includeTOF processing to provide TOF range information based on the AMmodulation of the reflection signal.

A multiple beam circuit can include a single laser and reference loop,with common optics for the multiple beams. The use of multiple transmitand receive/detection circuits can allow different beam steering andsweeping of different areas. In one example, the various transmit andreceive paths provided by circuits 1790 can be integrated onto the sameintegrated circuit or chip. In one example, the various transmit andreceive paths of circuits 1790 can be implemented as discrete componentscombined in parallel with common source and reference signals. In oneexample, different instances of optical circuits 1790 can implementdifferent types of modulation. Thus, multiple beams can combine anyexample of active or passive modulation structures.

In addition to multiple beams, or alternatively to multiple beams,different LIDAR systems can be used in parallel. For example, lasershaving different wavelengths can be used in parallel to perform sensingof a target.

FIG. 18 illustrates an example of a LIDAR system with an I/Qimplementation to distinguish AM information from FM information for aLIDAR signal. System 1800 represents an optical system in accordancewith embodiments of the present disclosure. The optical components canbe in accordance with any example herein to transmit an optical signalwith power and frequency modulation.

Generally, in an FMCW DSP (digital signal processing) chain, samplesfrom the ADC go through time domain filters for signal conditioning.Following time domain conditioning, a time-to-frequency domainconversion block (for example, an FFT (fast Fourier transform)) convertsthe time domain samples to frequency domain samples. In the frequencydomain, more filters can be applied to further condition/improve thesignal quality. After the frequency domain filtering, a frequency domainpeak picking algorithm is employed to estimate where the targets are.These peaks are a function of both the range and the relative Doppler ofthe target.

System 1800 represents a system with that generates a scanning beam thatincludes both FM and AM modulation. FM laser 1810 represents the FMCWsignal with FM modulation. The signal can be split with splitter 1820 toprovide AM modulation 1830 on the FM modulated signal, to generate an FMand AM modulated signal, which could also be referred to as a frequencyand power modulated signal. AM modulation 1830 can be active modulationin accordance with embodiments of active modulation of the presentdisclosure. AM modulation 1830 can be passive modulation in accordancewith embodiments of passive modulation of the present disclosure.Circulator 1840 can provide the modulated signal to lens system 1842 andscanner 1844 to transmit and receive signal reflections of targets in ascanned environment. System 1800 can include a PBS in place ofcirculator 1840.

System 1800 can provide an additional estimate of the range of thetarget with time domain processing as well as the frequency domainprocessing. Circulator 1840 can provide a received signal or signalreflection of the transmitted power and frequency modulated signal toI/Q (in-phase/quadrature) processor 1850, component, or other signalprocessor. The processor can use the frequency modulated signal fromsplitter 1820 as a reference to compare with the received signal fromcirculator 1840. In one example, I/Q processor 1850 has a balanced PD(photodetector) stage followed by an ADC stage.

In one example, I/Q processor 1850 includes two paths, one for AMmodulation and another for FM modulation. Balanced PD 1862 can feed toADC 1872 to generate an ‘x’ component. Balanced PD 1864 can feed to ADC1874 to generate a ‘y’ component. The combined processed signal allowsimprovement of the traditional FMCW signal information with additionalrange information from AM signaling, which can improve the target pointestimates. System 1800 can provide simultaneous detection of range andvelocity from the signal. System 1800 represents the AM signal componentwith the combiner after the ADC stage, with the signal represented asthe combination of x²+y².

FIG. 19 illustrates an example of a LIDAR system that provides FM and AMmodulation on a LIDAR signal. System 1900 provides an example of system1800. FMCW laser 1910 can be a laser transmission system in accordancewith any example herein that provides a light signal for both FM and AMmodulation. The modulation can be or include active AM modulation orpassive AM modulation. Optical components 1920 provide the modulationand optics to transmit TX signal 1912 to target 1930 and receive thereflection signal represented by RX signal 1932.

Photodetector 1940 can receive RX signal 1932 from optical components1920 from target 1930, and LO signal 1914 from optical components 1920from FMCW laser 1910. System 1900 can condition the signal with ADC 1950and provide the conditioned signal for digital signal processing 1960.In one example, digital signal processing 1960 generates point cloud1962, which can represent a group of points of estimates of targetinformation. A point cloud can refer to a group of target estimatevalues that have corresponding coordinate information to spatially mapthe points relative to each other.

System 1900 can generate an estimate of the range to the target(s) usinga time domain processing data path including a correlator and a delayestimator to measure ΔT. The time domain estimate of range can becombined with frequency domain peak information, to generate a morerobust estimate of range and velocity per point in the point cloud.

FIG. 20 illustrates an example of FQ detection for a LIDAR system thatprovides FM and AM modulation on a LIDAR signal. System 2000 illustratesI/Q detection for a receiver in accordance with an example of system1800 or DSP in accordance with an example of system 1900.

I/Q detection enables completely separating out AM and FM components ofa received signal. The X path is the In Phase signal (such as FQ 1850 tobalanced PD 1862 to ADC 1872 of system 1800) and the Quadrature signalis the Y path (such as I/Q 1850 to balanced PD 1864 to ADC 1874 ofsystem 1800). The in-phase signal is received at ADC 2010 whichgenerates the X component, which can be provided to compute block 2030and compute block 2040. The quadrature signal is received at ADC 2020which generates the Y component, which can be provided to compute block2030 and compute block 2040.

The processing can include calculations of X²+Y² for the AM signal andX/Y for the FM signal. Compute block 2030 can compute X²+Y² for AMsignal 2032 and compute block 2040 can compute X/Y for FM signal 2042.The computation of X/Y can lead to noise enhancement. In one example,system 2000 provides regularized division to mitigate noise enhancement.The regularized division can include a computation of X/(Y+Delta), whereDelta is an estimate adaptively based on signal and noise powers.

FIG. 21 illustrates an example of signal processing for an FM and AMmodulated signal. System 2100 illustrates FQ detection for a receiver inaccordance with embodiments of the present disclosure.

In some scenarios, the amplitude modulation (AM) part of the frequencymodulation (FM) can be extracted using an in-phase/quadrature (I/Q)detector following digital post processing. In one example, with postprocessing in the signal processing domain, the system can extract theAM portion and FM portion of the signal to separately estimate range andvelocity from a signal that simultaneously includes AM and FMinformation.

RX signal 2112 is the received signal or the reflected beam, whichincludes both an FM portion and an AM portion. LO signal 2114 is thelocal oscillator signal, which includes the FM portion of the signal. Inone example, the system uses the FM information of the LO signal in I/Qdetector 2110.

I/Q detector 2110 can generate signals E_(RX)+E_(LO) and E_(RX)−E_(LO)for a first balanced PD, represented by photodetector 2120, and signalsE_(RX)+e^(iπ/2)*E_(LO) and E_(RX)−e^(iπ/2)*E_(LO) for a second balancedPD, represented by photodetector 2130. Photodetector 2120 provides asignal output to ADC 2122, to generate an X signal that is proportionalto cos(ω_(AM))×cos(ω_(FM)). Photodetector 2130 provides a signal outputto ADC 2132, to generate a Y signal that is proportional tocos(ω_(AM))×sin(ω_(FM)). The LIDAR system can perform a computation X/Yfor FM and a computation X2+Y2 for AM, where the computations can bebased on the X and Y signals generated by system 2100.

FIG. 22 illustrates an example of an AM path and an FM path for FQdetection. System 2200 illustrates I/Q detection for a receiver inaccordance with embodiments of the present disclosure. System 2200provides a high-level schematic of a DSP architecture for simultaneousrange and velocity measurement based on a combined signal with AMmodulation and FM modulation. In addition to the estimate of range of atarget based on FMCW, system 2200 can provide an estimate based on timedomain processing.

The signal after time domain filters is tapped off and fed into analternate datapath, which aims to estimate dT (delta time) using timedomain processing. This datapath includes a correlator that either runsa correlation with a known time domain waveform or runs anautocorrelation of the time domain samples to estimate the delay betweenthe two T_off periods (beginning of a sweep (T_off)). A delay estimatortakes in the output of the correlator block and looks for peaks in thetime domain. These peaks correspond to the time-delay providing anestimate of the range of the target.

The signal can include in-phase portion 2202 and quadrature phaseportion 2204. In-phase portion 2202 has a path through ADC 2212 to AM/FMseparator 2220. In-phase portion 2202 can be portions of a signal thatare output from photodetector 2120 and/or ADC 2122 (depicted in FIG. 21). Quadrature phase portion 2204 can be portions of a signal that areoutput from photodetector 2130 and/or ADC 2132 (depicted in FIG. 21 ).Quadrature phase portion 2204 has a path through ADC 2214 to AM/FMseparator 2220. AM/FM separator 2220 can generate AM signal 2222 and FMsignal 2224. AM signal 2222 can be used to provide an estimate of therange with a time domain processing datapath, represented as AM datapath2230. AM datapath 2230 can include time domain filters 2232 forimproving SNR (signal to noise ratio) of the AM signal, time domaincorrelator 2234 to correlate the AM signal with an AM modulationwaveform reference, and delay estimator 2236 to estimate the TOF.

FM signal 2224 can be used to provide an estimate of range and Dopplershift with a frequency domain processing datapath, represented as FMdatapath 2240. FM datapath 2240 can include time domain filters 2242 toimprove SNR, time to frequency domain conversion 2244, frequency domainfilters 2246 to improve SNR, and frequency domain peak picking 2248 toestimate range and Doppler.

System 2200 combines the information from AM datapath 2230 and FMdatapath 2240. Joint range and velocity estimator 2250 represents acombination of the information from the two data processing paths, toprovide point cloud 2252 which represents a point set with estimates ofrange and velocity per point in a single measurement.

FIG. 23 illustrates an example of an AM path and an FM path for FQdetection with combined time domain filters. System 2300 illustrates I/Qdetection for a receiver in accordance with embodiments of the presentdisclosure. System 2300 provides a high-level schematic of a DSParchitecture for simultaneous range and velocity measurement based on acombined signal with AM modulation and FM modulation. In addition to theestimate of range of a target based on FMCW, system 2300 can provide anestimate based on time domain processing.

The signal after time domain filters is tapped off and fed into analternate datapath, which aims to estimate dT (delta time) using timedomain processing. This datapath includes a correlator that either runsa correlation with a known time domain waveform or runs anautocorrelation of the time domain samples to estimate the delay betweenthe two T_off periods (beginning of a sweep (T_off)). A delay estimatortakes in the output of the correlator block and looks for peaks in thetime domain. These peaks correspond to the time-delay providing anestimate of the range of the target.

The signal can include in-phase portion 2302 and quadrature phaseportion 2304. In-phase portion 2202 can be portions of a signal that areoutput from photodetector 2120 and/or ADC 2122 (depicted in FIG. 21 ).Quadrature phase portion 2204 can be portions of a signal that areoutput from photodetector 2130 and/or ADC 2132 (depicted in FIG. 21 ).In-phase portion 2302 has a path through ADC 2312 to AM/FM separator2320. Quadrature phase portion 2304 has a path through ADC 2314 to AM/FMseparator 2320. AM/FM separator 2320 can generate AM signal 2322 and FMsignal 2324. AM signal 2322 can be used to provide an estimate of therange with a time domain processing datapath, represented as AM datapath2330. FM signal 2324 can be used to provide an estimate of range andDoppler shift with a frequency domain processing datapath, representedas FM datapath 2340.

In one example, system 2300 includes time domain filters 2326 to applytime domain filtering to improve SNR of AM signal 2322 and FM signal2324. Time domain filters 2326 can provide AM signal 2322 to AM datapath2330. AM datapath 2330 can include time domain correlator 2334 tocorrelate the AM signal with an AM modulation waveform reference anddelay estimator 2336 to estimate the TOF. Time domain filters 2326 canprovide FM signal 2324 to FM datapath 2340. FM datapath 2340 can includetime to frequency domain conversion 2344, frequency domain filters 2346to improve SNR, and frequency domain peak picking 2348 to estimate rangeand Doppler.

System 2300 combines the information from AM datapath 2330 and FMdatapath 2340. Joint range and velocity estimator 2350 represents acombination of the information from the two data processing paths, toprovide point cloud 2352 which represents a point set with estimates ofrange and velocity per point in a single measurement.

FIG. 24 illustrates an example of in-phase detection for an FM and AMmodulated LIDAR signal. System 2400 illustrates I/Q detection for areceiver in accordance with the embodiments of the present disclosure.System 2400 represents processing for only an in-phase detector. Anin-phase detector can be used if I/Q detection is not a viable optiondue to hardware requirements or constraints on components such as ADCs.

System 2400 can separate the AM component from the received signal thathas AM and FM modulation, by the application of an envelope detector.In-phase portion 2402 can be portions of a signal that are output fromphotodetector 2120 and/or ADC 2122 (depicted in FIG. 21 ). In-phasesignal 2402 can be received at ADC 2410, which can generate FM signal2434. FM signal 2434 includes the FM signal information and will alsoinclude the AM signal information, which could cause degradation offrequency domain peak detection performance. In an implementation ofsystem 2400, keeping the AM signal bandwidth relatively small willmitigate performance loss.

FM signal 2434 can be sent to envelope detector 2420 to extract AMsignal information. Envelope detector 2420 can include a low pass filterfollowed by a magnitude detector to generate AM signal information,represented by AM signal 2432. AM signal 2432 and FM signal 2434represent the separated AM and FM signal portions of a combined signalfor simultaneous range and velocity estimation.

FIG. 25 illustrates an example of joint estimation from AM and FMdatapaths for concurrent range and velocity estimation. System 2500illustrates joint estimation for detection in accordance withembodiments of the present disclosure.

System 2500 receives a Peak_Freq input from an FM datapath, representedas Peak_Freq 2514, and a Delta_T input from an AM datapath, representedas Delta_T 2512. Delta_T 2512 can be portions of a signal that areoutput from envelope detector 2420 (e.g., AM signal 2432 depicted inFIG. 24 ). Peak_Freq 2514 can be portions of a signal that are outputfrom an ADC (e.g., FM signal 2434 depicted in FIG. 24 ). System 2500provides the inputs to joint range-velocity estimator 2510 to generatepoint map 2540. Joint range-velocity estimator 2510 receives Delta_T2512 at block 2520 to generate a map of Delta_T to range. Jointrange-velocity estimator 2510 receives Peak_Freq 2514 at block 2530 togenerate an estimate of range and velocity, which can be joined with themap of Delta_T to range from block 2520 to generate the joint estimationinformation, point map 2540.

Typically, Delta_T is mapped to range using an affine function, such asRange=C0*Delta_T+C1. Typically, peak frequency is a function of rangeand velocity using a function such as Peak_Freq=B0*Range+B1*Velo+B2.Given Delta_T and peak frequency, range and velocity can be estimated,given C0, C1, B0, B1, and B2 are calibrated per system. Estimates can beimproved by accounting for presence of noise in Delta_T and Peak_Freqestimates using regularized least squares estimation.

FIG. 26 illustrates an example an FM datapath processing for frequencypeak selection. Path 2602 represents a portion of an FM datapath. Path2602 receives FM signal 2610 at time domain filters 2620. Time domainfilters 2620 can provide the filtered signal to time to frequency domainconversion 2630, which provides the converted signal to frequency domainfilters 2640. After the application of frequency domain filters 2640,the signal in FM datapath 2602 is an FM signal in the frequency domain.FM datapath 2602 includes frequency peak picking 2650 to pick thestrongest peak in the frequency domain. The output of FM datapath 2602is Peak_Freq 2660.

The strongest peak's frequency depends on both range and relativeDoppler of the target. The peak detector of frequency peak picking 2650can employ additional techniques to improve probability of detection andfalse detection metrics. In one example, the peak detector only pickspeaks above a certain intensity or SNR. In one example, the peakdetector only picks peaks within a range of frequencies. In one example,the peak detector interpolates between two neighboring bins to improverange and velocity precision.

Diagram 2604 provides a diagrammatic representation of frequency (FREQ)versus peak signal detection (PSD). Signal 2672 represents the graphingof frequency versus PSD, and includes Peak_Freq 2674. Signal 2672 has afrequency limit 2676 based on the sampling rate. The sampling rate canbe twice the highest frequency of the anticipated signal (the Nyquistrate) to avoid aliasing of the signal. The peak frequency selected isthe highest peak based on the computations made.

FIG. 27 illustrates an example an AM datapath processing for time domaincorrelation. Path 2702 represents a portion of an AM datapath. Path 2702receives AM signal 2710 at autocorrelation 2720. AM signal 2710 can beportions of a signal that are output from an AM compute block (e.g.,compute 2030 depicted in FIG. 20 ). Autocorrelation 2720 generates AMautocorrelation 2730 to represent an auto-correlated AM signal output.

The AM autocorrelation indicates peaks at the range of the target, basedon the delay to the target. Diagram 2704 provides a diagrammaticrepresentation of the graphing of frequency versus autocorrelation.Signal 2742 represents the graphing of frequency versus autocorrelation.Peak frequency 2744 occurs at Delta_T, which is the time delayindicative of range to target. Signal 2742 has a frequency limit 2746based on the sweep duration.

FIG. 28 illustrates an example of AM datapath processing for time domaincorrelation when only a transmit path is modulated. Path 2802 representsa portion of an AM datapath. Path 2802 receives AM signal 2810 atcross-correlation 2820. AM signal 2810 can be portions of a signal thatare output from an AM compute block (e.g., compute 2030 depicted in FIG.20 ). Cross-correlation 2820 references modulation waveform 2850 as areference signal and generates AM cross-correlation 2830 to represent across-correlated AM signal output.

The AM cross correlation indicates peaks at the range of the target,based on the delay to target. Diagram 2804 provides a diagrammaticrepresentation of the graphing of frequency versus cross correlation.Signal 2842 represents the graphing of frequency versus crosscorrelation. Peak frequency 2844 occurs at Delta_T, which is the timedelay indicative of range to target. Signal 2842 has a frequency limit2846 based on the sweep duration.

FIG. 29 illustrates an example of delay estimation for AM signalcorrelation. A peak detector in the time domain provides an estimate ofDelta T. Time domain peak detection 2900 receives AM auto-correlation2910 (e.g., from path 2702 of FIG. 27 ) and AM cross-correlation 2920(e.g., from path 2802 of FIG. 2800 ) at delay estimator 2930. Delayestimator 2930 can generate the Delta_T output signal as an estimate oftime of flight.

Time domain peak detection 2900 can employ additional techniques toimprove a probability of detection metric and reduce a false detectionmetric. In one example, time domain peak detection 2900 only picks peaksabove a certain intensity/SNR. In one example, time domain peakdetection 2900 only picks peaks within a range of Delta_T values. In oneexample, time domain peak detection 2900 interpolates between twoneighboring samples to improve range precision.

FIG. 30 illustrates an example of a LIDAR system that provides FM and AMmodulation on a LIDAR signal. System 3000 provides an example of systemin accordance with embodiments of the present disclosure. System 3000includes LIDAR 3010, which represents a LIDAR system in accordance withany example herein.

In one example, LIDAR 3010 is an optical chip, which is coupled to aprocessor device or processor chip and a memory device or memory chip.In one example, system 3000 is a single device with LIDAR, processing,and memory components in a single device or device package. In oneexample, LIDAR 3010 is one of multiple LIDAR components coupled to aprocessing device.

LIDAR 3010 includes laser 3020, which can be a laser transmission systemin accordance with any example herein that provides an optical signalfor both FM and AM modulation. Optical circuit 3030 includes one or moreoptical circuit components or elements to provide modulation, referencesignaling, optical combining or other optical manipulation of an opticalsignal, amplification or attenuation, or other operation on an opticalsignal for LIDAR 3010. The modulation can be active or passive. Opticalcircuit 1730 provides the modulation and optics to transmit TX signal3022 to target 3040 and receive the reflection signal represented by RXsignal 3042. TX signal 3022 and RX signal 3042 include both FM and AMcomponents. The AM component can be TOF information provided by cyclingbetween baseline modulation power and a low power modulation, or can beprovided by encoding an AM signal onto an FM optical signal. Thereflection or RX signal will have the AM signal offset in time relativeto the transmit or TX signal.

Photodetector 3050 can receive RX signal 3042 from optical circuit 3030from target 3040, and LO signal 3024 from optical circuit 3030 fromlaser 3020. System 3000 can condition the signal with one or morecircuit components, represented by circuit 3060. In one example, circuit3060 includes an ADC component. Circuit 3060 can condition the receivedsignal detected by photodetector 3050.

Processor 3070 represents a processor device or processing unit.Processor 3070 can be a standalone component or be integrated in acomputer system. Processor 3070 includes FM processing 3072 and AMprocessing 3074 to represent the ability to extract FM information andAM information from the received signal detected by photodetector 3050.FM processing 3072 can be referred to as an FM datapath to generate FMrange values. AM processing 3072 can be referred to as an AM datapath togenerate AM range values. The FM information can enable processor 3070to compute information related to range, based on Doppler information orDoppler shift caused by a relative velocity of the target. Thus, FMprocessing 3072 can generate a Doppler-adjusted range value.

The AM information can enable processor 3070 to compute informationrelated to time of flight or signal delay information. Thus, AMprocessing 3074 can generate a range value corresponding to a signalpropagation delay between the LIDAR system and target 3040. Processor3070 can compute or determine a target range value for target 3040 basedon the AM range value. Processor 3070 can compute or determine a targetvelocity value for target 3040 based on a difference between theDoppler-adjusted range value and the AM range value.

The values generated can be part of a point cloud of information to mapan environment of target 3040. In one example, system 3000 includesmemory 3080 coupled to processor 3070 to store information computed byprocessor 3070, and to provide data for computation by processor 3070.In one example, memory 3080 stores point cloud 3082, to represent theinformation gathered by scanning target 3040 with LIDAR 3010. Pointcloud 3082 can be or include estimates or values computed by processor3070 based on scanning target 3040.

In one example, optical circuit 3030 includes an active modulator thatcan determine a start to the period of time for the low-power mode basedon receipt of a control signal at the active modulator. In one example,optical circuit 3030 includes an active modulator and LIDAR 3010includes multiple photodetectors. In such an example, the activemodulator can determine a start to the period of time for the low-powermode based on receipt of a control signal at a different photodetector,other than photodetector 3050. For example, LIDAR 3010 can include acontrolling photodetector and one or more subsidiary detectors.

In general with respect to the descriptions herein, in one example, alight detection and ranging (LIDAR) system includes: a frequencymodulation (FM) modulator to FM modulate a light signal as an FMmodulated signal; an active modulator to provide time of flight (TOF)signal information with the FM modulated signal as a power and frequencymodulated signal; an emitter to emit the power and frequency modulatedsignal; and a detector to receive a reflection of the power andfrequency modulated signal and provide a detected signal for signalprocessing to generate a target point set, including frequencyprocessing to generate target points based on range and Dopplerinformation, and TOF processing to provide TOF range information.

In one example of the LIDAR system, the FM modulator is to selectivelyturn FM modulation off for a pulse. In accordance with any precedingexample of the LIDAR system, in one example, the FM modulation is to beturned off for the pulse during a frequency up sweep. In accordance withany preceding example of the LIDAR system, in one example, the FMmodulation is to be turned off for the pulse at a beginning of atransition from frequency down sweep to frequency up sweep. Inaccordance with any preceding example of the LIDAR system, in oneexample, the FM modulation is to be turned off for the pulse during afrequency down sweep. In accordance with any preceding example of theLIDAR system, in one example, the FM modulation is to be turned off forthe pulse at a beginning of a transition from frequency up sweep tofrequency down sweep. In accordance with any preceding example of theLIDAR system, in one example, the TOF signal information comprises anamplitude modulation (AM). In accordance with any preceding example ofthe LIDAR system, in one example, the active modulator comprises aMach-Zehnder modulator (MZM). In accordance with any preceding exampleof the LIDAR system, in one example, the active modulator comprises anoptical attenuator. In accordance with any preceding example of theLIDAR system, in one example, the active modulator comprises an opticalcircuit to AM modulate an optical amplifier gain signal. In accordancewith any preceding example of the LIDAR system, in one example, thedetector comprises an in-phase/quadrature (I/Q) detector to extract anAM part of the reflection and an FM part of the reflection. Inaccordance with any preceding example of the LIDAR system, in oneexample, the LIDAR system includes: a splitter to send the FM modulatedsignal into a transmit (TX) path and a local oscillator (LO) path;wherein the active modulator is in the TX path to provide the TOF signalinformation on the frequency modulated signal for transmission, and theLO path is not provided with the TOF signal information.

In general with respect to the descriptions herein, in one example, amethod includes: modulating a light signal with frequency modulation(FM) to generate an FM modulated signal; encoding the FM modulatedsignal with a time of flight (TOF) signal with an active modulator togenerate an FM and AM modulated signal; emitting the FM and AM modulatedsignal; and processing to a reflection of the FM and AM modulated signalto generate a target point set, including frequency processing togenerate target points based on range and Doppler information, and TOFprocessing to provide TOF range information.

In one example of the method, modulating the light signal includesselectively turning FM modulation off for a pulse. In accordance withany preceding example of the method, in one example, modulating thelight signal includes turning off for the pulse during a frequency upsweep. In accordance with any preceding example of the method, in oneexample, modulating the light signal includes turning off for the pulseat a beginning of a transition from frequency down sweep to frequency upsweep. In accordance with any preceding example of the method, in oneexample, modulating the light signal includes turning off for the pulseduring a frequency down sweep. In accordance with any preceding exampleof the method, in one example, modulating the light signal includesturning off for the pulse at a beginning of a transition from frequencyup sweep to frequency down sweep. In accordance with any precedingexample of the method, in one example, the TOF signal informationcomprises an amplitude modulation (AM). In accordance with any precedingexample of the method, in one example, the active modulator comprises aMach-Zehnder modulator (MZM). In accordance with any preceding exampleof the method, in one example, the active modulator comprises an opticalattenuator. In accordance with any preceding example of the method, inone example, the active modulator comprises an optical circuit to AMmodulate an optical amplifier gain signal. In accordance with anypreceding example of the method, in one example the method includes,extracting an AM part of the reflection and an FM part of the reflectionan in-phase/quadrature (I/Q) detector. In accordance with any precedingexample of the method, in one example, the method includes: sending theFM modulated signal into a transmit (TX) path and a local oscillator(LO) path; wherein the active modulator is in the TX path to provide theTOF signal information on the frequency modulated signal fortransmission, and the LO path is not provided with the TOF signalinformation.

In general with respect to the descriptions herein, in one example, alight detection and ranging (LIDAR) system includes: a light source togenerate a light signal; an optical circuit including a frequencymodulation (FM) modulator to FM modulate the light signal as an FMmodulated signal; an active modulator to provide time of flight (TOF)signal information with the FM modulated signal as a power and frequencymodulated signal; an emitter to emit the power and frequency modulatedsignal; a detector to receive a reflection of the power and frequencymodulated signal; and a processing device to apply processing to thereflection to generate a target point set, including frequencyprocessing to generate target points based on range and Dopplerinformation, and TOF processing to provide TOF range information; andoptics to transmit the power and frequency modulated signal from theoptical circuit and provide a reflection of the power and frequencymodulated signal to the detector.

In one example of the LIDAR system, the FM modulator is to selectivelyturn FM modulation off for a pulse at a beginning of a transition fromfrequency down sweep to frequency up sweep. In accordance with anypreceding example of the LIDAR system, in one example, the FM modulatoris to selectively turn FM modulation off for a pulse at a beginning of atransition from frequency up sweep to frequency down sweep. Inaccordance with any preceding example of the LIDAR system, in oneexample, the TOF signal information comprises an amplitude modulation(AM). In accordance with any preceding example of the LIDAR system, inone example, the active modulator comprises a Mach-Zehnder modulator(MZM), an optical attenuator, or an optical circuit to AM modulate anoptical amplifier gain signal. In accordance with any preceding exampleof the LIDAR system, in one example, the TOF signal informationcomprises an amplitude modulation (AM). In accordance with any precedingexample of the LIDAR system, in one example, the optical circuitcomprises a first optical circuit, and further comprising a secondoptical circuit, wherein the first and second optical circuits are tomodulate the light signal, and wherein the optics is to transmit powerand frequency modulated signals from the first optical circuit andsecond optical circuit, and provide reflections of the power andfrequency modulated signals to the detectors for processing. Inaccordance with any preceding example of the LIDAR system, in oneexample, the LIDAR system includes: a splitter to send the FM modulatedsignal into a transmit (TX) path and a local oscillator (LO) path;wherein the active modulator is in the TX path to provide the TOF signalinformation on the frequency modulated signal for transmission, and theLO path is not provided with the TOF signal information.

In one example of the LIDAR system, the TOF range information can beused by an automobile, motorcycle, bicycle, scooter, helicopter, orplane; automated driver assist systems in an automobile, motorcycle,bicycle, scooter, helicopter, or plane; or self-driving vehicle such aspart of an automobile, motorcycle, bicycle, scooter, helicopter, orplane.

Besides what is described herein, various modifications can be made tothe disclosed examples and implementations of the invention withoutdeparting from their scope. Therefore, the illustrations and examplesherein should be construed in an illustrative, and not a restrictivesense.

What is claimed is:
 1. A frequency modulated continuous wave (FMCW)light detection and ranging (LIDAR) system, comprising: an opticalsource to transmit a light signal; an active modulator to modulate thelight signal with a low-power mode at a section of a sweep signal togenerate a pulsed light signal transmitted towards a target; aphotodetector to receive a return beam from the target based on thepulsed light signal, the return beam comprises an amplitude modulated(AM) signal portion and a frequency modulated (FM) signal portion; and aprocessor coupled to the photodetector configured to: determine a targetrange value for the target based on the AM signal portion; and determinea target velocity value for the target based on the FM signal portion.2. The FMCW LIDAR system of claim 1, wherein the FM signal portioncomprises a first FM signal portion, and further comprising: the activemodulator to modulate a portion of the light signal to produce a secondFM signal portion transmitted towards a local oscillator; and thephotodetector to combine the second FM signal portion with the first FMsignal portion to determine the target velocity value.
 3. The FMCW LIDARsystem of claim 1, wherein the active modulator is further to: modulate,for a period of time, the light signal at the section of the sweepsignal, wherein the section is after a transition from an upsweep signalto a downsweep signal.
 4. The FMCW LIDAR system of claim 1, wherein theactive modulator is further to: modulate, for a period of time, thelight signal at the section of the sweep signal, wherein the section isafter a transition from a downsweep signal to an upsweep signal.
 5. TheFMCW LIDAR system of claim 1, wherein the active modulator is furtherto: modulate, for a period of time, the light signal at the section ofthe sweep signal, wherein the section is after a transition betweenupsweep and downsweep has settled.
 6. The FMCW LIDAR system of claim 1,wherein the low-power mode comprises the active modulator to turn off FMmodulation of the light signal for a period of time.
 7. The FMCW LIDARsystem of claim 1, wherein the active modulator comprises a Mach-Zehndermodulator (MZM).
 8. The FMCW LIDAR system of claim 1, wherein the activemodulator comprises an optical attenuator.
 9. The FMCW LIDAR system ofclaim 1, wherein the active modulator comprises an optical circuit tomodulate an optical amplifier gain signal.
 10. A method for lightdetection and ranging (LIDAR), comprising: transmitting a light signal;modulating, with an active modulator, the light signal with a low-powermode at a section of a sweep signal to generate a pulsed light signaltransmitted towards a target; receiving a return beam from the targetbased on the pulsed light signal, the return beam comprising anamplitude modulated (AM) signal portion and a frequency modulated (FM)signal portion; and determining a target range value for the targetbased on the AM signal portion; and determining a target velocity valuefor the target based on the FM signal portion.
 11. The method of claim10, wherein the FM signal portion comprises a first FM signal portion,and further comprising: modulating a portion of the light signal toproduce a second FM signal portion transmitted towards a localoscillator; and combining the second FM signal portion with the first FMsignal portion to determine the target velocity value.
 12. The method ofclaim 10, wherein modulating the light signal at the section of thesweep signal comprises: modulating, for a period of time, the lightsignal at the section of the sweep signal, wherein the section is aftera transition from an upsweep signal to a downsweep signal.
 13. Themethod of claim 10, wherein modulating the light signal at the sectionof the sweep signal comprises: modulating, for a period of time, thelight signal at the section of the sweep signal, wherein the section isafter a transition from a downsweep signal to an upsweep signal.
 14. Themethod of claim 10, wherein modulating the light signal at the sectionof the sweep signal comprises: modulating, for a period of time, thelight signal at the section of the sweep signal, wherein the section isafter a transition between upsweep and downsweep has settled.
 15. Themethod of claim 10, wherein modulating the light signal with thelow-power mode comprises: turning off FM modulation of the light signalfor a period of time.
 16. A light detection and ranging (LIDAR) system,comprising: a light source to generate a light signal; an opticalcircuit comprising: an optical source to transmit the light signal; anactive modulator to modulate the light signal with a low-power mode at asection of a sweep signal to generate a pulsed light signal transmittedtowards a target; and a photodetector to receive a return beam from thetarget based on the pulsed light signal, the return beam comprising anamplitude modulated (AM) signal portion and a frequency modulated (FM)signal portion; a processing device coupled to the photodetectorconfigured to: determine a target range value for the target based onthe AM signal portion; and determine a target velocity value for thetarget based on the FM signal portion; and optics to transmit the pulsedlight signal from the optical circuit and direct the return beam to thephotodetector.
 17. The LIDAR system of claim 16, wherein the FM signalportion comprises a first FM signal portion, and further comprising: theactive modulator to modulate a portion of the light signal to produce asecond FM signal portion transmitted towards a local oscillator; and thephotodetector to combine the second FM signal portion with the first FMsignal portion to determine the target velocity value.
 18. The LIDARsystem of claim 16, wherein the active modulator is further to:modulate, for a period of time, the light signal at the section of thesweep signal, wherein the section is after a transition between anupsweep signal and a downsweep signal.
 19. The LIDAR system of claim 16,wherein the active modulator is further to: modulate, for a period oftime, the light signal at the section of the sweep signal, wherein thesection is after a transition between upsweep and downsweep has settled.20. The LIDAR system of claim 16, wherein the low-power mode comprisesthe active modulator to stop FM modulation of the light signal for aperiod of time.